The present invention relates to an image forming apparatus having a sheet cassette. More particularly, the invention relates to such sheet feed cassette which stores therein a stack of a plurality of sheets for supplying each one of sheets to an image forming section of an image forming apparatus with avoiding diagonal sheet feeding.
A conventional sheet feed cassette of this kind is provided in an image forming apparatus such as a printer and a copying machine etc., for storing therein a stack of a plurality of sheets. The printer is provided with sheet supplying roller for feeding out, one by one, an uppermost sheet of the sheet stack stored in the sheet feed cassette. Within the sheet feed cassette, sheet lifter plate is provided for bringing the sheet stack into contact with the sheet supplying roller when the sheet cassette is attached to the printer. Further, within the sheet feed cassette, sheet guides are provided at lateral sides thereof, so that lateral side edges of the sheets are in contact therewith for the purpose of guiding the sheet in a sheet feeding direction directing toward a printing section.
However, if sheets are voluminously stacked to a height approximately equal to the upper edge of the sheet guide in the sheet feed cassette, and such cassette is assembled into the printer, the upper sheet(s) of the sheet stack may exceed over the upper edge of the sheet guide due to the movement of the sheet lifter toward the sheet supplying roller. If sheet feed out operation is carried out with such a state by the sheet supplying roller, the upper sheet may not undergo guiding by the sheet guides. Therefore, diagonal sheet feeding may occur. Such diagonal sheet feeding may cause sheet jamming, and largely degrade printing quality.